In a computer system such as a personal computer, a card-edge connector assembly is used for providing electrical connection between a main wiring board and an optional wiring board. Typical of such a connector assembly is a two-piece assembly which consists of plug and socket members to be coupled together between main and optional wiring boards. Problems are encountered by such a two-piece connector assembly principally because of the fact that prior-art two-piece connector assemblies manufactured on a standardized, large-scale production basis are ordinarily such that the plug and socket members of a connector assembly share in the the number of contact pins with each other. The present invention contemplates provision of an improved connector assembly free from such problems.